Very few of us are racing...
Very few of us are racing on an unlimited budget, and one of the best ways to get the most out of your racing program is to handle your wreck repairs yourself, whenever possible.
Accidents happen. It's a fact of life--especially when it comes to stock car racing. Fortunately, unlike a bad credit rating, stock cars are often easily fixed. Because it can be so difficult to get all the suspension points back in the correct spots, replacing a front or rear clip should often be left to the chassis builder, but replacing a bent bar or two can often be handled by most racers.
At first glance, when trying to determine exactly how to repair frame damage, the complex pattern of rollcage and other frame tubing can be a bit intimidating. Some bars may intersect and be welded to other bars in several locations along its length. Fortunately, for the round tubing supporting the front and rear clip, it often isn't necessary to completely remove the entire length of a piece of tubing that has been damaged. Instead, only the section that has been deformed can be cut away and a new bar spliced in its place. Splicing two pieces of tubing so that it is as strong as a single piece isn't difficult, but it does require a few tricks.
To find out exactly how it should be done, we travelled to Hess Racecars in Mooresville, N.C. Hess Racecars specializes in asphalt chassis-everything from Late Models to Busch and Nextel Cup cars-but the techniques will work on any piece of round tubing. Also, it should be emphasized that splicing tubing anywhere in the main rollcage shouldn't be attempted by an amateur welder. In fact, most professional chassis builders will only splice a few specific bars in a few specific places on the main rollcage. It is simply better to replace the entire length of tubing rather than take a chance on the splice not holding. Let's follow along as Hess' Chris Cornett splices in a new bar.
Hess Racecars was in the process...
Hess Racecars was in the process of replacing this front clip. It had taken a hit on the left-front corner and shifted everything to the right. Both down tubes were bent a bit, and the bung locations needed to be changed for an update, so they were cut in the first straight section above the main bend.
Here's a shot of the chassis...
Here's a shot of the chassis up on one of Hess Racecars' jigs. This chassis has been completely stripped, but that isn't necessary if you are just performing localized repairs. Just make sure you have access to weld all the way around the tubing in question.
Replacing an entire front...
Replacing an entire front clip, like is being done here, should probably be left to your chassis builder, but the same procedures are used on smaller repairs. As you can see, everything that has been damaged has been cut away before any repairs begin. The upper tubes to be spliced have already been prepped by sanding away the powder coat for approximately three inches. It is also important that your cuts are clean and square. This is no time to be using the plasma cutter.
When cutting and bending your...
When cutting and bending your tubing to replace the damaged section, always use the same size and gauge steel. Also, remember to leave approximately 1/8-inch gap at the splice to allow weld penetration to the slug. When choosing a splice location, it is best to find a straight section of tubing at least two to three inches long. It is possible to splice along a curved section of tubing, but it's much more difficult to get everything to fit right.
Fabricator Chris Cornett checks...
Fabricator Chris Cornett checks his tubing one last time to make sure it fits up exactly like the old section did.
Cornett drills four holes...
Cornett drills four holes into the tubing on each side of the splice. These are for rosette welds that will greatly add to the splice's strength. Cornett recommends your holes be at least 3/8-inch in diameter.
Here, you can see the slug...
Here, you can see the slug in place. Cornett says it should be the tightest fit you can get and the same wall thickness as your main tubing. For example, this car uses 1 3/4 DOM mild steel tubing with 0.095-inch wall thickness. So the slug is 1 1/2 DOM mild steel with the same wall thickness. The wall thickness is important not only to add strength to the splice but also to ensure you do not burn through the metal when making your rosette welds. Finally, the slug should be long enough to extend past your holes on both sides by at least 1/2-inch. This slug was approximately four inches in length.
With a small tack holding...
With a small tack holding the slug in place inside the main chassis tube, Cornett checks again to make sure his patch tube still fits properly into position.
Once everything is properly...
Once everything is properly positioned, Cornett adds another tack to hold both tubes with the proper gap between them.
Using a MIG welder, Cornett...
Using a MIG welder, Cornett welds with the wire touching the slug. The heat must be turned up high enough on the welder that it is capable of fusing both the slug along with the ends of the tubing on both sides. That's why the width of the gap is important. It must be wide enough so that the wire can reach the slug, but close enough so that both ends of the tubing get hot as well. Cornett also adds that he always begins his weld at the bottom of the tube and works his way up. This way he is always working at the edge of the weld puddle. If you start at the top and work your way down, gravity can pull the weld puddle into your work area and keep you from getting good weld penetration.
Next come the rosette welds....
Next come the rosette welds. Hold the tip of the welder perpendicular to the hole and work your way around in a circle until the hole you have drilled into the tubing is completely filled with the weld puddle.
Cornett says when making your...
Cornett says when making your rosette welds not to be afraid to turn the voltage up on your welder. You have to make sure the weld really burns into the slug, but because of the wall thickness you don't have to worry about burning through. Also, Cornett says he uses his ears as much as his eyes when making his rosette welds. Once the weld puddle rises above the thickness of the outer tube the sound changes and he knows to stop.
Here's the completed weld....
Here's the completed weld. You can tell from the color of the metal that a lot of heat has been put into it. But it is necessary to make sure both pieces of tubing and the slug are properly fused. All weld beads should extend just beyond the diameter of the tubing. Any weld that sinks below the tubing isn't good enough.
It isn't structurally necessary,...
It isn't structurally necessary, but for the sake of neatness, Cornett sands down the weld beads until they are smooth with the tubing. Just don't go crazy with a grinder here.
Here's the completed stitch...
Here's the completed stitch ready for paint or powder coat.
Obviously, there is still...
Obviously, there is still a lot of work to be done before this chassis will be ready to return to the racetrack, but you can see the value of stitching the down tube where we did. This particular bar extends through the firewall and ends at a multiple-joint at the A-pillar. Stitching the tubing where Cornett chose produced a repair that is just as strong as replacing the entire piece of tubing, plus it saved him a lot of time and his customer a lot of money.
Hess Racecars
704/799-6740